Demilec Attic Air Sealing: The Fresno Owner’s Guide
If you’ve got Demilec spray foam in your attic and you’re noticing drafts, dust, or a sudden jump in your cooling bill, the air seal has likely failed and we can fix it. We stock Demilec-compatible air sealing materials on our trucks and install them throughout Fresno, with most attic air sealing jobs running between $1,200 and $3,800 depending on square footage and how much of the existing seal needs to be cut out and redone. Most Fresno jobs are completed in a single day, and we typically schedule within three to five days of your call.
Here’s how most homeowners find the problem: a room that never quite cools on a 105-degree Fresno afternoon, a fine gray dust settling on boxes in the attic, or an energy bill that’s 20% higher than the same month last year with no other changes. The air seal goes quiet when it fails. You don’t hear a pop or a crack. The foam just starts pulling away from the framing, hairline gaps open up, and conditioned air leaks into the attic while 140-degree attic air leaks back down into the house. By the time you notice it, it’s been failing for a while.
Key takeaways:
- We stock Demilec-compatible air sealing materials for same-week installation in Fresno
- Typical attic air sealing runs $1,200 to $3,800; you get a written price before we touch anything
- Most air seal failures happen at the joint between the foam and the wood framing, especially after a hot Fresno summer
- Every job is covered by our 365-Day Done Right Promise in writing
Which Demilec Models This Applies To
Demilec air sealing in attics is typically done with their open-cell spray foam line, most commonly Heatlok HFO and Sealection 500. We also see a fair number of Fresno homes with Demilec’s older Sealection 400 and Heatlok Soy 200, particularly houses built or retrofitted between 2005 and 2015. The air sealing part of the job isn’t a separate Demilec product number you’ll find on a shelf. It’s the foam itself, applied to the full attic floor or roofline, plus the bead work around penetrations: plumbing vents, recessed light housings, wiring chases, and the top plates where interior walls meet the attic.
Here’s the compatibility gotcha most people miss: if your attic was sealed with an open-cell Demilec product, you need to replace it with another open-cell product of similar density. Swapping in a closed-cell foam over open-cell creates a different vapor profile and can trap moisture against the framing. That’s a rot risk in Fresno’s hot-dry summers followed by foggy winters, when temperature swings drive condensation. We match the replacement material to the original application. We also carry Reflectix for homeowners who want a radiant barrier supplement in specific situations, but for a failed Demilec air seal, the fix is properly installed spray foam, not a reflective roll.
Identifying what you have is straightforward enough. The original installer usually left a work order or invoice in the attic or garage. If not, open-cell Demilec foam is soft and spongy when you press it with a finger, light tan or off-white, and you can see tiny open bubbles in the surface. Closed-cell is rigid, darker, and smooth. We’ll confirm what’s up there before we quote anything, because guessing at the chemistry is how you end up paying for the same job twice.
Signs Your Demilec Attic Air Sealing Is Failing
- Rooms that won’t hold temperature. The air seal’s job is to stop attic air from mixing with house air. When it fails, the upstairs bedrooms and any room under a vaulted ceiling start swinging five to ten degrees from the thermostat setting. This is the one Glenn Hartley hears most from Fresno homeowners in July and August.
- Attic dust in the house. A broken air seal lets fine blown-in insulation and years of settled dust drift through ceiling cracks and around light fixtures. If you’re wiping gray film off the tops of ceiling fan blades every week, that’s not normal house dust. It’s attic dust migrating through failed seals.
- Energy usage that doesn’t match the weather. Pull your last July bill against the same month two years ago. If the rate plan’s the same and the bill’s up 20% or more, your attic is losing conditioned air somewhere. Fresno’s PG&E territory has some of the highest summer rates in the state, so a failed seal is money leaking every hour the AC runs.
- Foam pulling away from framing. In a properly sealed attic, the foam sits tight against every stud, rafter, and top plate. Walk up there with a flashlight and look along the roof deck. If you see cracks running through the foam or gaps where the foam has separated from the wood by a quarter inch or more, the seal is gone and the insulation value drops with it.
- Pest droppings or nesting in the foam. Rodents and birds find open-cell foam easy to tunnel through once it’s exposed. If you see droppings along the roofline or burrowed holes in the foam, you’ve got a two-part problem: the air seal is gone and something is living in the cavity where it used to be.
Replacement Cost & What’s Included
For a typical Fresno home with an attic footprint between 1,200 and 2,200 square feet, replacing a failed Demilec air seal runs $1,200 to $3,800 installed. The spread comes down to a few things: how much of the existing foam needs to be cut out and replaced versus spot repaired, whether we’re resealing just the attic floor or the full roofline, and how accessible the problem areas are. A Tower District bungalow with a cramped, low-pitch attic costs more in labor than a newer Clovis tract home with a walkable truss system, even if the square footage is similar.
Everything’s in the written quote before we start. No materials surcharge that shows up at the door. No “we found something extra” mid-job conversation that doubles the bill. The price includes the foam, disposal of any cut-out material, clean-up, and our written guarantee. If it’s not right within 365 days, we come back and fix it at no charge. That’s the Kingswell Guarantee, and it’s included on every single job, in writing.
DIY or Call Us?
There are things you can safely check yourself, and there are things that go wrong fast when you try to do them with a can from the hardware store. Here’s the honest split. You can absolutely go into your attic with a flashlight and check for visible gaps, black staining around sheathing, or foam that’s crumbled into piles. That’s a useful inspection, and it’ll tell you whether you should call someone. What you should not do is attempt to reseal an existing Demilec open-cell installation with store-bought foam in a can. Single-component foam cures differently, doesn’t expand to the same profile, and won’t bond properly to the aged Demilec surface. You’ll spend a weekend crawling through a hot attic and the seal will fail again by next spring.
Spray foam work in an attic also means working around electrical, recessed lights, and in our climate, attic temperatures that hit 150 degrees by 10 a.m. in summer. Our crew wears proper respiratory protection and knows how to stage the work so the foam cures correctly. If you’re seeing the signs, call us at (559) 785-2658 and we’ll take a look. The diagnosis is free, and you’ll know exactly what you’re dealing with before you spend a dollar.
FAQs
A properly installed Demilec open-cell air seal should last 20 to 30 years in a Fresno attic, but we see failures at the 8 to 12 year mark when the original install was rushed or the attic has poor ventilation. The extreme heat cycling we get in the Central Valley, with summer attic temps pushing 150 degrees and winter nights dropping into the 30s, accelerates foam separation at the framing joints. Call us at (559) 785-2658 if you want an honest assessment of what’s still in good shape up there.
In most Fresno attics, we can cut out and replace sections where the foam has separated from the framing without redoing the entire space. Partial repairs work when the failure is localized, which it often is at top plates and around penetrations. If the foam has failed across more than half the roofline or floor, replacement of the full area is usually cheaper per square foot than chasing individual gaps. We’ll show you what we’re seeing before we quote it.
Most Fresno attic air seal replacements are done in one day, including cutting out the failed material, prepping the surfaces, spraying the new foam, and cleaning up. Large attics over 2,000 square feet or jobs requiring extensive removal can take two days. You’ll get a committed arrival window in writing before we start, and a live person answers our phone 24/7 if you have questions during the job.
Yes. We carry Demilec-compatible open-cell foam, seam tapes, and air seal gasketing on our trucks, so we don’t have to order materials and reschedule your job. Woolsey Insulation Fresno is an independent service provider, not affiliated with Demilec, but we work with their materials alongside seven other insulation brands so the recommendation fits your attic, not whatever happens to be on the truck. Call (559) 785-2658 and we’ll tell you what’s in stock for your specific situation.
If your Demilec attic air seal has failed, the fix is straightforward: we match the right open-cell foam to your existing installation, cut out what’s failed, and reseal it properly. Look before you quote – every attic tells you something the paperwork won’t. Call Woolsey Insulation Fresno at (559) 785-2658 for a free assessment and a written price before any work starts. Glenn Hartley and our crew serve homeowners throughout Fresno, Clovis, and the surrounding Central Valley.
Written by Glenn Hartley, Owner, Woolsey Insulation Fresno at Woolsey Insulation Fresno, serving Fresno and nearby areas.